Herpesviruses are ubiquitous in humans and they have been implicated in diverse malignancies. Human Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus are associated with tumors of lymphoid, epithelial, and endothelial origin in immuno-compromised patients. Due to a paucity of human studies and lack of permissive cell lines and animal models, host immune responses and in vivo infection of KSHV and EBV are largely unknown. Being closely-related KSHV and EBV, murine 3- herpesvirus 68 (3HV68) infects mice, replicates to higher titers in the lung and establishes persistent latent infection in the spleen, providing an excellent tractable animal model to delineate the entire immune responses and viral infection in vivo. Upon viral infection, host innate immune pathways are often activated to induce the production of antiviral inflammatory cytokines and interferons. Using 3HV68 as a model for KSHV and EBV, we have recently discovered that 3HV68 hijacks an innate immune pathway to promote viral lytic replication and to prevent antiviral cytokine production. Thus, we will investigate the molecular mechanisms by which 3HV68 deploys to activate the host innate immune signaling pathway to promote viral transcriptional activation in Aim 1 and to subvert antiviral cytokine production in Aim 2. Furthermore, we will delineate the virus-host interactions that activate the innate immune pathway in Aim 3. Collectively, this study will elucidate a novel mechanism whereby 3HV68 infection activates a host innate immune signaling pathway to enable viral transcription and disable host cytokine production, thereby greatly expanding our current paradigm of immune subversion. Findings gleaned from this study will advance our understanding of host activation and viral exploitation of innate immune responses, and potentially guide our future efforts in vaccine design and antiviral therapeutics to treat malignancies associated with human KSHV and EBV. PUBLIC HEALTH RELEVANCE: The aims of this study are to investigate the molecular mechanisms by which a host innate immune pathway is exploited to facilitate viral infection and to delineate the virus-host interactions that activate the innate immune pathway. Thus, this study will advance our understanding of pathogen immune exploitation, host innate immune responses, and viral pathogenesis. Findings from our study will re-shape our view of "antiviral innate immunity", provide an animal model for studies using human tumorigenic herpesviruses, and also potentially guide future efforts to treat herpesvirus-associated malignancies.!